1. Field of the Invention
This invention relates generally to roll-up awnings for travel trailers or recreational vehicles, and in particular to a roller tube which forms the front of the awning assembly.
2. Description of the Related Art
It has long been recognized roll-up awnings have been useful in the recreational vehicle field. Such awnings are particularly useful when trailer homes or recreational vehicles are parked at a campsite. While parked, there is a need for a protected area in which users may take cover from inclement weather. A spring-biased, roll-up awning has long been used in the field.
A roll-up awning generally comprises a canopy connected at one end to the side of the recreational vehicle, and at the opposite end connected to a roller tube. The roller tube is pivotally supported by extended arms which are pivotally mounted to the side of the recreational vehicle. In a stored position, the canopy is rolled about the roller tube and secured to the recreational vehicle's side wall. When the awning is in use, the canopy is unrolled and is supported by the roller tube which is in turn supported by the extended side arms. In the unrolled position, the roller tube must not only support the weight of the canopy, but also the weight of other attachments (such as a screen or a valance), as well as resist the forces of nature (such as wind and rain). A roller tube, therefore, must be able to resist significant amounts of both normal force and bending stress.
In the past, when the awning was of long span, the roller tube would sag between its end supports. This situation was remedied by adding extra supports or by increasing the strength of the roller tube. One method of increasing the strength of a roller tube is to fabricate the tube from extruded aluminum. Extruded aluminum roller tubes have performed satisfactorily but are expensive to manufacture. Extruded steel roller tubes are also known in the art. However, because awnings are usually exposed to the elements, it is desirable to use steel which is electrogalvanized on both sides and specially coated for corrosion resistance. Extrusion does not permit the use of electrogalvanized or precoated steel. Furthermore, steel extrusion requires a steel having a lower yield strength than is suitable for awning support.
To reduce costs and improve performance, it is preferable to roll form the awning tube using a high strength material which is galvanized and painted prior to forming. Roll forming of aluminum is possible, but requires a softer and lower strength aluminum which is not adequate for awning support applications. Roll formed steel tubes are known which are welded or otherwise fastened. Typically, these use rivets or other elaborate means to fasten the awning to the tube. Roll formed tubes joined by welding at their seams are known. The weld or other fastener creates a bump in the rolled awning, tends to degrade the material and destroys corrosion resistant coatings.
Another non-extruded roller tube is shown in U.S. Pat. No. 4,258,778. The roller tube is fabricated from roll-formed steel and includes an injected plastic brace which increases the tube's resistance to bending forces. Such roller tubes are fabricated by folding and crimping the ends of the sheet metal together into a lock joint. The lock joint is located between slideways on the outer circumference of the roller tube. The placement of the lock joint on the circumference has been found to create problems of imbalance when the awning is being rolled out and rolled in. During rotation the tube has a greater deflection than is desirable. Twisting of the tube tends to cause relative axial sliding of the interlocking seam parts.
It is desirable, for corrosion resistance and aesthetic purposes, to have an awning assembly including a roller tube which is roll formed of previously galvanized, specially coated and painted steel. Such a roller tube reduces the awning's maintenance and increases its aesthetic value. The tube must have sufficient strength to support an awning and withstand other variable forces. Furthermore, its cross section should provide characteristics which properly balance the tube and minimize deflection during rolling and unrolling of the awning.
The object of the present invention is to provide a roll formed roller tube which is inexpensive to manufacture while providing the strength and balance characteristics required by current awning designs. The tube should be adaptable to a wide variety of spring loaded awnings, and can be incorporated into existing awning designs.